Large-size panel of thermoplastic synthetic resin for automotive vehicle interior, and process for the production thereof

ABSTRACT

A large-size paneling part made of thermoplastic synthetic resins for automotive vehicle interiors or equivalent uses includes a support made of polyolefin particle foam onto which is laminated a decorative layer of polymeric material having a predominantly polyolefin structure during forming of the molded part. This decorative layer includes a multilayer knit mesh or woven fabric with incorporated spacers of preferably polyolefinic polymer threads, having a decorative textile surface. This layer may be laminated on the topside with a decoratively designed film, predominantly on the basis of olefinic polymers or, respectively, be laminated additionally on the rear side with a polyolefin film.

BACKGROUND OF THE INVENTION

The invention relates to large-size paneling parts of a thermoplasticsynthetic resin for the interior of an automotive vehicle, and to aprocess for the production thereof.

Panels for the interior of an automotive vehicle along the lines of thisinvention are understood to mean, in particular, door side parts,headliners (finished dome liners), seat back linings, hat shelves, andside paneling of thermoplastic synthetic resins.

Molded parts as paneling parts in multilayer structure for uses inautomotive vehicle interiors have been known for a long time. Suchconstructions usually consist of a compact supporting member ofthermoplastic or thermosetting synthetic resins filled with variousmaterials, or of fibrous starting materials converted, with the aid ofsuitable resins, into a mechanically load-bearing composite; see, inthis connection, for example DOS 3,842,846.

The actual shaping process takes place according to the conventionalmethods primarily by press-molding, injection molding or in accordancewith the RIM and, respectively, RRIM technology.

The basic components display the joint feature that their surface meetsonly very low decorative requirements. Decorative paneling members areobtained from these molded parts by joining these basic materials withdecorative, flat products during the shaping step or also in separateprocedures. These decorative, flat products can be imprinted andembossed plastic sheeting as well as woven, knit textiles or nonwovens.

In case a composite is produced by subsequent lamination, the bondbetween the decorative and, in some cases, soft and elastic top layerand the supporting molded member must be established with simultaneousapplication of pressure and heat and with the use of a speciallaminating material.

In pressing processes, flat products are placed into the tool utilizedfor the shaping step, and thereafter molded parts are produced havingdecorative, soft and elastic surfaces. Materials that can be processedaccording to the presently known techniques, and molded partsmanufactured pursuant to such techniques exhibit a number ofdisadvantages:

The pressure to be expended during the press-molding step for thenonwoven mat production step ranges above 5-10 bar, in case of injectionmolding even above several hundred bar.

The materials employed normally are not based on a unitary polymer typeso that the conventional molded parts can be recycled only forlow-quality products.

The mass temperature during the shaping step lies, in case ofthermoplastic materials, above 180°-200° C. and therefore leads tothermal damage to the top material in cases where the latter is notespecially protected, for example by a film, foam sheet, or a similarmaterial.

Molded parts produced in this way must be refinished in a second workingstep in order to produce a rounded border.

SUMMARY OF THE INVENTION

It is an object of the present invention to provide a structure for amolded part which no longer exhibits the aforementioned drawbacks of theconventional structures and makes it possible to obtain decorativesurfaces of a higher quality.

In order to attain this object, the invention proposes to fashion apaneling member of thermoplastic synthetic resin. The molded parts ofthis invention are characterized particularly in that, during theprocess of shaping the molded part, a decorative layer of polymershaving predominantly a polyolefinic structure is applied by laminating,this layer consisting of a multilayer knit or woven fabric withincorporated spacers of preferably polyolefinic polymer threads, andhaving a decorative, textile surface, or being laminated additionally onthe topside with a decorative film--predominantly on the basis ofolefinic polymers--or, respectively, is additionally laminated on therear side with a polyolefin film. Another version resides in the use ofa two-ply decorative layer of an outside compact layer and foamedsheeting, especially of a polyolefin. Preferred structures of thepaneling members are molded parts of several layers (sandwichcomponents), all based on the same polymer (preferably polyolefins) withsoft, grained, or textile surfaces. The structure of the molded partspursuant to the invention here ensures the prerequisites for theintended usage with respect to the prescribed technical specificationsaccording to the present status. The disclosed process for producing themolded parts is economical and advantageous. The process provides anoptically pleasing and esthetic design of the surfaces and offers a widevariation possibility.

In the process of this invention, the posed objective has been attainedaccording to a process wherein the decorative layer is formed in aseparate working step and is thereafter placed in a mold having walls ofa microporous material, the decorative layer being shaped and embossedin the mold by application of a vacuum. Subsequently, pre-expandedpolyolefin particles are loaded into the mold and are expanded to form asupport for the decorative layer and to bond with the decorative layer.

The invention achieves a reduction of the total weight of the sandwichcomponent (support plus decorative layer) for paneling members by atleast 50%.

By applying the technique described in DOS 4,008,173, varying densitiesin the supporting member of the molded part can also advantageously beattained for the present invention.

In addition, the present invention solves the recycling problem forthese parts in that only components are utilized which are built up on acommon, recyclable polymer basis.

Preferably, the decorative material employed is a compact film inconjunction with foam sheeting or with a spacer fabric mesh, with orwithout a coating on the topside.

These materials used in accordance with the invention have the featurein common that they consist of jointly recyclable polyolefins and/orpolyolefin composites, just as the thin layer optionally provided ontheir underside, being of the same material also used for the expandableplastic granulated substance for the basic material of the support.Consequently, the additional application of an adhesion-promoting layeras the laminating layer between the decorative layer and the supportingmember is eliminated.

Conventional expandable synthetic resin granules (beads) are employed asthe basic material for the supporting layer, consisting of thermoplasticsynthetic resins, optionally with proportions of blowing gas, and beingpre-expanded. Suitable thermoplastic resins are, for example,polyethylene (PE) of medium density and polypropylene (PP) which cancontain, if desired, further auxiliary agents, such as stabilizers,pigments, fillers, etc., as well as copolymers of polyolefins orcompounds of homo- and copolymers. The size of these pre-expandedgranules is about 2-5 mm. The shape of these granules is spherical orapproximately spherical.

Preferably, the respectively identical plastic is utilized for the basicmaterial and the sheeting.

The mold utilized according to this invention is made from a microporousmaterial displaying on the inside the desired surface texture as anegative of the subsequent molded part.

The production of such molded parts is also described in thespecification of DE 38 42 846 A1. In this disclosure, the surface is tobe produced in the soft-elastic range by the pressure of the foam beadsand the subsequent vapor pressure. Based on the indicated operatingtemperatures and mode of operation, a thermally stable embossing ortexturing of the surface cannot be expected. Also the use of amicroporous mold is disclosed in this laid-open application, but merelyfor the extraction of air and moisture.

In contrast to this patent, a positive mold is utilized according to theprocess of this invention, the surface of this mold carrying the grainedtexture of the finished part. Galvanic molds are primarily used for thispurpose, manufactured in correspondence with Patent DE 37 43 809 C2. Bythe application of a vacuum, the heated-through decorative layer isapplied by suction to the surface and embossed; in this procedure, thedecorative layer and the mold wall can optionally be preheated to closeto below the crystallite melting temperature of the surface material inorder to produce a clean and thermally stable grained texture.

After formation of the decorative layer, the granules (beads) are filledin the cold or slightly preheated condition into a mold equipped withsteam-supplying nozzles through which superheated steam can beintroduced with a temperature of about 130° C. and under a pressure ofabout 6 bar.

After the mold has been filled, it is closed, and the granules areheated, expanded and fused according to the conventional method.

An essential feature of this invention is the use of a decorative layerbased on a moldable material, such as a nonwoven mat or a fabric or aknit material, optionally with spacers or an expanded polyolefinsheeting or such a sheeting consisting of a multilayer structurerepresenting a laminate of compact and foamed polyolefin sheets, thegrained texture of which on the decorative side is produced bydeep-drawing in correspondingly designed vacuum molds provided with thenegative embossing.

The basis for the decorative layer is constituted primarily by a mesh ofpolyolefin fibers of differing denier, also called spacer mesh.Preferably, fibers are used with a denier of between 0.5 and 1.5 dtex.The mesh is produced so that its thickness ranges between 0.4 and 2.5 mmwith a density of below 0.5 g/cm¹.

The structure of the spacer mesh consists chracteristically of at leasttwo knit layers joined together by means of pile threads, the so-calledspacers, manufactured according to conventional methods of thedouble-rib loom technique. In addition to the spacing of the two layersand thus also the thickness of the total layer, it is possible toadjust, within wide limits, the elongation, elasticity and strength ofsuch a mesh.

These spacer meshes are optionally laminated on one side with a sheetingof polyolefins (thermocompression bonding) and embossed in the sameoperating step with the use of a textured microporous vacuum die as themold. The embossing depth ranges between 60 and 150 μm. The color of thesheeting can be set as desired. Embossing of the sheeting can take placeeither beforehand with engraved steel rolls under pressure or,alternatively, in the mold by means of an appropriate mold surface andwith the use of vacuum.

In case a textile surface is desired, the top film can also be omitted.In this case, knit or woven fabrics are used, the topside of which hasalready been provided with a corresponding design during the knittingstep.

Alternatively, smooth films without embossing can be utilized which canbe embossed subsequently in conjunction with the mesh or the foamsheeting, for example in accordance with a vacuum technique.

The total structure of the decorative layer, including the filmslaminated thereon, corresponds in its properties to the PVC foamsheeting used nowadays but, in contrast to the latter, is madecompletely on the basis of one polymer, for example polyolefins, andtherefore fulfills, along the lines of this invention, the requirementfor uniformity of material.

After the molded parts have been produced, they can be processed and/orenhanced in further working steps, in a similar way as this is done withconventional parts.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a cross-sectional view of one embodiment of the inventioncontaining fabric material within the decorative layer; and

FIG. 2 shows a cross-sectional view of another embodiment of theinvention containing polymeric foam sheeting in the decorative layer.

DETAILED DESCRIPTION OF THE INVENTION

One embodiment for a molded part having the structure of this inventionfor use as a paneling member is illustrated in FIG. 1. In thisillustration, the basic part, namely the supporting member 1, producedfrom expanded polyolefin particles, is bonded to a film 2 of the samematerial as the supporting member and with a spacer mesh 3 with pilethreads 5 of polyolefin and a compact layer 4 of a polyolefin. Thelayers 3, 4 form the decorative layer with a backing layer constitutedby the film 2.

Other possible structures of a paneling member consist, for example, ofa supporting member 1, a film 2, and a spacer mesh 3 with a textiledecorative surface. Another version is represented, for example, by apaneling member of a supporting member 1 and a decorative layer 4.

FIG. 2 shows a further embodiment of the paneling member according tothis invention. The paneling member is a laminate consisting of asupporting layer 1 of PP particle foam, an intermediate layer 6 ofextruded PP foam sheeting, and a compact PP decorative film 4. Theindividual layers are cemented together by suitable adhesives 7; thedecorative film (top layer) is sealed with flat varnish 8.

In the present process, the particle foam and the decorative layers areproduced in different processes and bonded in a further process. The PPfoam layer 6 and the decorative layer 4 are bonded and, after sealingthe front side and application of the adhesive and/or of a primer to therear side, are vacuum molded in accordance with the form of thesupporting layer 1. In the same working step, this composite is bondedto the supporting layer 1.

The invention will be described in greater detail with reference topractical examples.

EXAMPLE 1

A decorative layer consisting of a spacer mesh laminated to adecoratively designed film based on a polyolefinic compound is insertedin a microporous mold, preheated, preferably to about 110°-130° C., andthereafter brought into contact with the mold surface through themicroporous walls thereof with a vacuum pressure of about 0.8 bar. Theedges and corners of this decorative layer were previously foldedinwardly for this purpose and provisionally fixed in place.Subsequently, pre-expanded granules of polypropylene are poured into themold cavity lined with the decorative layer, the mold is closed, andbonding is effected by the action of steam, pressure and heat so thatthere is achieved, on the one hand, a bond in the manner of a weldingbond among the foam granules and, on the other hand, a bond of the foamgranules to the decorative layer in contact therewith. The wallthickness of the molded part is, at the thinnest point, about 3 mm and,at the thickest point, about 7 mm. The surface area of the molded partis about 1.2 m².

The granules are in this case filled into the microporous mold andbonded, with steam having a temperature of 142° C. and under a pressureof 3.5 bar, to form a flat molded part 1, the granules being expanded atthe same time.

EXAMPLE 2

A decorative layer consisting of a spacer mesh laminated with anuntextured polyolefin film is placed into a microporous mold with atextured surface. By preheating with infrared and application of avacuum, the film is pulled into the microporous mold together with thespacer mesh in such a way that the texturing of the mold surface forms apermanent embossing in the film. Thereafter, as described in Example 1,the molded part is finished up.

EXAMPLE 3

A spacer mesh decorated on the topside by the application of a designand laminated on the rear side with a thin film as a sealing layer madeof polypropylene is inserted in a microporous mold and then kept inplace by suction and preformed until it is in contact with the surfacesof the mold. Then, as described in Example 1, the molded part is formedby introduction of polypropylene foam granules and subsequent expansion.

What is claimed is:
 1. A large-size panel of thermoplastic syntheticresin for the interior of an automotive vehicle which comprises a moldedpart comprising a support and a decorative layer, said supportconsisting of polyolefin particle foam onto which the decorative layercomprising a polyolefin structure, is secured by laminating duringshaping of the molded part, said decorative layer comprising amultilayered knit mesh or woven fabric having incorporated thereinspacers of polyolefin threads, consisting of at least two knit layersjoined together by said spacers and being laminated optionally on thetopside with a decoratively designed film predominantly comprising anolefin polymer to provide a decorative textile topside and on the rearside with a polyolefin film, and said support being laminated to saiddecorative layer during foaming of the polyolefin particle foam.
 2. Themolded part according to claim 1, wherein the molded part exhibitsvarying densities throughout the support and the decorative layer ofbetween 0.1 and 0.4 g/cm².
 3. The molded part according to claim 1,wherein the molded part is formed to have a surface area of up to 2.5m².
 4. The molded part according to claim 1, wherein the molded part hasa thickness between 1.5 mm and 100 mm.
 5. The molded part according toclaim 1, wherein the decorative layer comprises a spacer knit mesh ofpolyolefin fibers having a denier of between 0.5 and 1.5 dtex.
 6. Themolded part according to claim 1, wherein the weight per unit area ofthe decorative layer ranges between 0.1 and 0.5 g/cm².
 7. The moldedpart according to claim 1, wherein the decorative layer has a thicknessof between 0.4 mm and 2.5 mm.